attachMovie variables

programming flash
1

When I click on a button, I want to attach a movie from the library to (x,y) coordinates set up in the movie I’m attaching.

To clear that up a bit:

I have a movie clip in the library with a linkage name my_mc.
my_mc has two variables (startx, starty) declared in it’s timeline.
On the main timeline I have a button with instance name my_btn.
I’m trying to do something like this:

my_btn.onRelease = function(){[INDENT]     _root.attachMovie("my_mc","mc",1000);
    mc._x = mc.startx;
    mc._y = mc.starty;
[/INDENT]};

This, however, fails miserably.